Thermal processing method and apparatus therefor

Abstract

An Si 3 N 4 layer is formed on a surface of a wafer, which is an object to be processed, at a high temperature of, for example, 780° C., using a vertical thermal processing apparatus having a reaction tube of a double-wall structure comprising an inner tube and an outer tube in which a predetermined reduced-pressure status is maintained within the reaction tube while a reaction gas comprising, for example, SiH 2 Cl 2 and NH 3 is made to flow from an inner side to an outer side of the inner tube by the action of a first gas supply pipe and first exhaust pipe provided in the thermal processing apparatus. Next, the temperature in the interior of the reaction tube is raised to, for example, 1000° C., a reaction gas comprising, for example, H 2 O vapor and HCl is made to flow from the outer side to the inner side of the inner tube by the action of a second gas supply pipe and second exhaust pipe, and an SiO 2 layer is formed by the oxidation of the surface of the Si 3 N 4 layer formed on the surface of the wafer, under normal-pressure conditions. The use of a combined chamber enables the implementation of film formation and either oxidation or diffusion processing without having to remove the object to be processed from the reaction tube, and thus prevents the intrusion of a natural oxide layer or the incorporation of particles into a thin film structure of, for example, SiO 2 and Si 3 N 4 layers used as a multi-layer insulating film for devices such as DRAMs.

What is claimed is: 
     
       1. A method of thermally processing an object to be processed, using a vertical thermal processing apparatus provided with a reaction tube of a double-wall structure having an inner tube and an outer tube, wherein a first gas supply pipe and a second exhaust pipe are provided so as to open into an inner side of said inner tube and a second gas supply pipe and a first exhaust pipe are provided so as to open into a space between said inner tube and said outer tube, said thermal processing method comprising the following steps in order: (A) a first step of using said first gas supply pipe and said first exhaust pipe to make a processing gas flow from said inner side of said inner tube to an outer side thereof, to form a film on a surface of said object to be processed in a heated, reduced-pressure environment; and   (B) a second step of using said second gas supply pipe and said second exhaust pipe to make a processing gas flow from said outer side of said inner tube to said inner side thereof, to perform oxidation or diffusion processing on said surface of said object to be processed in a heated, normal-pressure environment.   
     
     
       2. A method of thermally processing an object to be processed, using a vertical thermal processing apparatus provided with a reaction-tube of a double-wall structure having an inner tube and an outer tube, wherein a first gas supply pipe and a second exhaust pipe are provided so as to open into an inner side of said inner tube and a second gas supply pipe and a first exhaust pipe are provided so as to open into a space between said inner tube and said outer tube, said thermal processing method comprising the following steps in order: (A) a second step of using said second gas supply pipe and said second exhaust pipe to make a processing gas flow from an outer side of said inner tube to said inner side thereof, to perform oxidation or diffusion processing on said surface of said object to be processed in a heated, normal-pressure environment; and   (B) a first step of using said first gas supply pipe and said first exhaust pipe to make a processing gas flow from said inner side of said inner tube to said outer side thereof, to form a film on a surface of said object to be processed in a heated, reduced-pressure environment.   
     
     
       3. A method of thermally processing an object to be processed, using a vertical thermal processing apparatus provided with a reaction tube of a double-wall structure having an inner tube and an outer tube, wherein a first gas supply pipe and a second exhaust pipe are provided so as to open into an inner side of said inner tube and a second gas supply pipe and a first exhaust pipe are provided so as to open into a space between said inner tube and said outer tube, said thermal processing method comprising the following steps in order: (A) a first step of using said first gas supply pipe and said first exhaust pipe to make a processing gas flow from said inner side of said inner tube to an outer side thereof, to form a film on a surface of said object to be processed in a heated, reduced-pressure environment;   (B) a second step of using said second gas supply pipe and said second exhaust pipe to make a processing gas flow from said outer side of said inner tube to said inner side thereof, to perform oxidation or diffusion processing on said surface of said object to be processed in a heated, normal-pressure environment; and   (C) repeating said first step.   
     
     
       4. A method of thermally processing an object to be processed, using a vertical thermal processing apparatus provided with a reaction-tube of a double-wall structure having an Inner tube and an outer tube, wherein a first gas supply pipe and a second exhaust pipe are provided so as to open into an inner side of said inner tube and a second gas supply pipe and a first exhaust pipe are provided so as to open into a space between said inner tube and said outer tube, said thermal processing method comprising the following steps in order: (A) a second step of using said second gas supply pipe and said second exhaust pipe to make a processing gas flow from an outer side of said inner tube to said inner side thereof, to perform oxidation or diffusion processing on said surface of said object to be processed in a heated, normal-pressure environment;   (B) a first step of using said first gas supply pipe and said first exhaust pipe to make a processing gas flow from said inner side of said inner tube to said outer side thereof, to form a film on a surface of said object to be processed in a heated, reduced-pressure environment; and   (C) repeating said second step.   
     
     
       5. The thermal processing method of any one of claims 1 to 4, wherein said first step is a step for forming a silicon nitride layer and said second step is a step for oxidizing a surface of a formed silicon nitride layer to form a silicon oxide layer. 
     
     
       6. The thermal processing method of any one of claims 1 to 4, wherein a further step of purging atmosphere within said reaction tube with nitrogen gas is performed between said first step and said second step.